I've recently attempted to wipe free space from both my hard drives - a solid state (64gig) and also ordinary drive (500gig), using the latest version of Eraser. Almost 24 hrs later it still isn't complete. I suspect it is due to the painfully slow speeds of writing small files to flash drives.
I'm wondering if I create one large truecrypt file to take up the rest of the drive space, then delete it. Would this have a similar effect as free space software?

I took a look at Eraser's description at download.com and it seems to do secure wipes, overwriting a space several times. So just deleting a big file does not work the same way. Besides, you don't know how Truecrypt creates the file, it may simply allocate the space from free space but leave the original data/junk intact until you use That space.

Besides, you don't know how Truecrypt creates the file, it may simply allocate the space from free space but leave the original data/junk intact until you use That space.

Actually yes you do, and no it doesn't Truecrypt overwrites the space by encrypting random data, giving a result which is theoretically undistinguishable from true random data -- as long as the underlying encryption algorithm (AES by default) isn't broken.

The difference here would be the number of times that the data is physically overwritten on the disk -- Truecrypt will only write one pass.

I think it is basically depend on the hard drive space. If you have less space into the OS drive then the load of the services were very much to handle the operation and take very much time to complete so you need to remove unnecessary processes after then you can see the result.

Just FYI - you need to have very *SPECIAL* equipment in order to recover information from a hard drive that has been fully rewritten once. This kind of equipment is very expensive and I doubt any of us will be of that interest, in order for our hard drives to end up in such forensics lab. So don't waste your time and only rewrite the hard drive once.

Agreed. I am a computer forensic examiner. One pass is sufficient to render the data unrecoverable. There is a technique that can be used to recover data that has been wiped but it is very expensive and has a low success rate.